Armenian police have detained the opposition leader Nikol Pashinyan as protests against the former president Serzh Sarksyan’s appointment as prime minister entered a tenth day.

Police said Pashinyan was forcibly taken from a rally on Sunday, shortly after Sarksyan rejected demands to step down, as riot police and demonstrators clashed in the capital. Nearly 200 protesters were also detained.

Demonstrators accuse Sarksyan of clinging to power following 10 years as president. Tens of thousands of opponents have marched through Yerevan in recent days, blocking streets in the city centre and staging sit-ins.

Under a revised constitution approved in a 2015 referendum, most state powers in the small, former Soviet state have shifted to the prime minister and the presidency has become a largely ceremonial post. Opponents say the shift effectively makes Sargsyan Armenia’s leader for life.

Sarksyan met Pashinyan, the opposition politician leading the protests, in Yerevan on Sunday but left talks a few minutes after their talks began.

“This is not talks, not a dialogue. It’s just an ultimatum, blackmail of the state, of the legitimate authorities,” Sarksyan told Pashinyan.

He said the opposition had failed to learn the lesson of 1 March, referring to a protest rally after his re-election in 2008 when 10 people were killed in clashes with police.

“No one has dared and will dare speak to us in the language of threats. I am telling you, you have no understanding of the situation in the country. The situation is different to the one you knew 15-20 days ago,” Pashinyan told Sarksyan.

“The situation in Armenia has changed, you don’t have the power of which you are told. In Armenia, the power has passed to the people,” he said.

Pashinyan then vowed to step up pressure on Sarksyan to force him to resign. He was detained hours after the encounter.

“Despite repeated calls to stop illegal rallies, Pashinyan continued leading a demonstration,” police said in a statement, adding that he and two other opposition MPs were forcibly taken from the site as riot police dispersed the rally. They dismissed reports that Pashinyan had been arrested.

Sasun Mikaelyan, an opposition MP, earlier told journalists that Pashinyan had been arrested. “People must liberate Nikol,” he said.

As an MP, Pashinyan is protected by a parliamentary immunityand cannot be arrested without its approval, according to the constitution.

Opposition supporters have criticised 63-year-old Sarksyan over poverty, corruption and the influence of powerful oligarchs in the landlocked South Caucasus nation of 2.9 million people.

More than 70 people were arrested on Saturday, according to authorities, including two people suspected of preparing bombs. In the evening, about 50,000 demonstrators gathered in the capital’s central Republic Square.